This invention relates to engine monitoring apparatus.
The invention is more particularly concerned with apparatus for detecting abnormal start conditions of a gas-turbine engine.
During start-up procedures of a gas-turbine engine, the pilot or flight engineer (where the engine is in an aircraft) monitors a number of instruments giving details of various engine characteristics, such as N 1 and N 2 spool speeds, exhaust gas temperature EGT, and fuel flow. It is important for the engine operation to be carefully monitored during start-up because gas-turbine engines can be prone to abnormal or `hot` starts which can lead to irreparable damage to an engine at a cost of up to about one million pounds. Some aircraft operators experience several such hot starts each year.
It will be appreciated that, at the time of starting the engine, the flight crew are faced with many other tasks as well as monitoring for hot starts. With some engines it can take up to a minute for the engine to start and for the risk of hot start to be passed. The detection of hot start relies on the flight crew's ability accurately to assess the instrument readings, to remember the various limits of operation that may be indicative of a hot start and to identify exceedance of these limits and take appropriate action. The flight crew's ability to do this while undertaking other activities can be restricted.